Spabking plug



June 14, 1949. c. M. cARlNGToN E'rAl. 2,473,241

sP-ARKING PLUG Filhed Nov. 29, 1944 v lNvENroRs CHARLES MoLYNEUx CARINGTON &

Patented June 14, 1949 SPARKING PLUG Charles Molyneux Carington and George William Shoobert, London,

England,

assignors to K. L. G. Sparking kPlugs Limited, London, England, a British company Application November 29, 1944, Serial No. 565,585 In Great Britain August 17, 1943 Section 1, Public Law 690, August 8, 1946 Patent expires August 17, 1963 5 Claims. 1

This invention relates to sparking-plugs. It has been found that in some circumstances of use, for example on aero-engines, sparking-plugs are subject to intense vibration including vibration of a very high frequency which is deleterious to the mechanical construction of the plug. In plugs in which a ceramic insulator is used for the central electrode, this electrode is secured in the body of the plug by gripping an enlargement of the insulator which is situated between its ends, near the middle of its lengthso that the two ends of the insulator project therefrom and are unsupported laterally, since it is desirable to provide an air-space around them. The outer end of the plug, that is to say the end carrying the terminal to which the high-tension lead is connected, is in some circumstances of substantial length and being unsupported laterally the vibration effects above mentioned have been found in some cases to cause a fracture or failure of the upper end yof the insulator, and the object of the present invention is to provide an improved construction whereby such failures are prevented.

The accompanying drawing which illustrates this invention is a central longitudinal section of a sparking-plug and associated screening tube.

The main body of the plug is indicated at I with a ceramic insulator Il which is secured in place by means of an enlargement I2 of the insulator which is gripped between an internal shoulder I3 on the body of the plug and the openended member I4 which is screwed into the body of the plug. The usual screening tube I5 is secured in the member I4, and is provided with an internal layer of insulating material I6. The central electrode Il of the plug is secured in the insulator in any convenientmanner. It will be seen that the insulator is supported in the body of the plug only at the enlargement I2 so that the end I8 is unsupported laterally and is therefore subject to the vibration effects above mentioned. In order to damp out or reduce the vibration, there is provided an expansible collar or ring-like member 24 which is secured to the end of the electrode I1 and presses outwardly against the inner surface or lining of the screening tube I5. Conveniently this member is mainly barrelshaped and has an inturned flange 25 which is gripped under a flange on the end of the electrode. For this purpose two washers 26, 21 may be threaded on to the end of the electrode with the flange 25 between them, a spring washer 25a being disposed under the flange 25, and the hollow end of the electrode is spun over at 28 to retain the washers and flange 25 in place by pressure against the end of the insulator I8.

The central hole in the inturned flange 25 of the barrel-ring 2t is larger than the diameter of the electrode I'I, and the third Washer of springy material and of corrugated yor dished form may be inserted with the flange 25 between the washers 26, 2l so that it exerts axial pressure on the flange 25, and by friction thereon restrains any relative lateral movement between the insulator, and the screening tube I5.`

We claim:

l. In a sparking-plug, the combination of a body, a ceramic insulator secured therein only at a point between its ends whereby the ends of the insulator are unsupported laterally, a screening tube secured on said body and surrounding but spaced radially from the end of said insulator, a barrel-shaped member engaging the inner surface of said screening tube, an inturned flange of said barrel-shaped member, and a pair of washers secured on said insulator frictionally engaging said inturned flange between them.

2. In a sparking-plug, the combination of a body formed with an internal shoulder, a ceramic insulator having an enlargement between its ends engaging said shoulder, a nut clamping said insulator against said shoulder, a screening tube rigidly secured on said nut surrounding but spaced radially from the end of said insulator, an electrode rigidly secured in said insulator, and projecting from the end thereof, a hollow barrelshaped member engaging the inner surface of said screening tube, an inturned flange on said member, a washer threaded on the end of said electrode engaging the end of the insulator, a spring washer engaging said first-mentioned washer on one side and engaging said inturned flange on the other side, and a third washer secured on said electrode pressing said inturned flange against said spring washer.

3. In a sparking plug, the combination of a body formed with an internal shoulder, a ceramic insulator formed with laterally extending shoulders between its ends, one of said shoulders engaging the shoulder of said body, a nut screwed into said body and engaging the other shoulder of the insulator, a casing rigidly secured to said body and surrounding the end of the insulator in radially spaced apart relationship, a central electrode in said insulator, a hollow ring-like member engaging the inner surface of said casing and secured to the end of said insulator.

4. In sparking plugs having a body, a ceramic insulator firmly fastened in the body so that an end of the insulator extends outwardly from the body and a screening tube rigidly secured to the body in radially spaced apart relationship about the extended end of the insulator, a hollow barrelshaped member engaging the screening tube, an inturned ange on said member adapted to engage the end of the insulator and fastening means for attaching the iiange to the insulator end.

5. In sparking plugs having a body, with an internal shoulder therein, a ceramic insulator having an enlargement intermediate its ends engaging said shoulder and a screening tube threaded into the body and surrounding one end of the insulator in radially spaced apart relationship, a hollow barrel-shaped member engaging the inner surface of the screening tube, an inturned flange on said member, adapted to engage the end of the insulator and fastening means for attaching the iiange to the insulator end.

CHARLES MOLYNEUX CARINGTON. GEORGE WILLIAM SHOOBERT.

REFERENCES CITED The following referenbes are of record in the le of this patent:

UNITED STATES PATENTS Great Britain 1902 

